How to Implement Biometric Authentication in a Flutter App (The Right Way)

In today's world, security is no longer optional - it's expected. Whether it's a fintech app, a fitness tracker, or an internal company tool, users want fast and secure access without the hassle of remembering passwords. That's exactly where biometric authentication comes in. In this guide, we'll walk through how we implement biometric authentication in a Flutter app , the practical approach we follow in production, and the common mistakes developers often make (and how to avoid them). Why Biometric Authentication? Before jumping into implementation, let's quickly understand why it matters: Faster login experience (no typing passwords) More secure than traditional authentication Native support across Android & iOS Better user trust and retention What We Use in Flutter To implement biometric authentication, we rely on: local_auth package (official Flutter plugin) Native biometric APIs under the hood (Face ID, Touch ID, Fingerprint) Step 1: Add Dependency dependencies : local_auth : ^3.0.1 Then run: flutter pub get Step 2: Platform Setup ✅ Android Setup Inside android/app/src/main/AndroidManifest.xml : <uses-permission android:name= "android.permission.USE_BIOMETRIC" /> Also ensure: <uses-feature android:name= "android.hardware.fingerprint" android:required= "false" /> ✅ iOS Setup Inside ios/Runner/Info.plist : <key> NSFaceIDUsageDescription </key> <string> We use Face ID to authenticate you securely </string> ⚠️ Without this, Face ID will NOT work and your app may crash. Step 3: Implement Biometric Logic Here's how we structure it in production: import 'package:flutter/foundation.dart' ; import 'package:local_auth/local_auth.dart' ; class BiometricService { final LocalAuthentication _auth = LocalAuthentication (); /// Check if device supports biometrics Future < bool > isBiometricAvailable () async { try { final bool canCheckBiometrics = await _auth . canCheckBiometrics ; final bool isDeviceSupported = await _auth . isDeviceSupported (); return canCheckBiometrics &&